Note 8 – Property, Plant and Equipment

Our property, plant and equipment, net, consisted of the following (in thousands):

	December 31,			December 31,
	2017			2016
Machinery, equipment, vehicles and office furniture	$	4,251,711		$	2,154,367
Tooling		1,255,952			794,793
Leasehold improvements		789,751			505,295
Land and buildings		2,517,247			1,079,452
Computer equipment, hardware and software		395,067			275,655
Construction in progress		2,541,588			2,147,332
Other		—			23,548
		11,751,316			6,980,442
Less: Accumulated depreciation and amortization		(1,723,794	)		(997,485	)
Total	$	10,027,522		$	5,982,957

Construction in progress is primarily comprised of tooling and equipment related to the manufacturing of our vehicles and a portion of Gigafactory 1 construction. In addition, construction in progress also included certain build-to-suit lease costs incurred at our Buffalo manufacturing facility, referred to as Gigafactory 2. Completed assets are transferred to their respective asset classes, and depreciation begins when an asset is ready for its intended use. Interest on outstanding debt is capitalized during periods of significant capital asset construction and amortized over the useful lives of the related assets. During the years ended December 31, 2017 and 2016, we capitalized $124.9 million and $46.7 million, respectively, of interest.

As of December 31, 2017 and December 31, 2016, the table above included $1.63 billion and $1.32 billion, respectively, of build-to-suit lease assets. As of December 31, 2017 and December 31, 2016, the corresponding financing liabilities of $14.9 million and $3.8 million, respectively, were recorded in accrued liabilities and $1.67 billion and $1.32 billion, respectively, were recorded in other long-term liabilities.

Depreciation and amortization expense during the years ended December 31, 2017, 2016 and 2015 was $769.3 million, $477.3 million and $278.7 million, respectively. Gross property and equipment under capital leases as of December 31, 2017 and December 31, 2016 was $688.3 million and $112.6 million, respectively. Accumulated depreciation on property and equipment under capital leases as of these dates was $100.6 million and $40.2 million, respectively.

We had cumulatively capitalized costs of $3.15 billion and $1.04 billion, respectively, for Gigafactory 1 as of December 31, 2017 and December 31, 2016.